1. Field of the Invention
The present invention relates to rotary electric machines, with homopolar structure, also called transverse flux electric machines, composite or the like, very generally including a stator and rotor, and in particular able to be housed in a carcass. The at least one stator and rotor is made up of at least one electric coil supported by a magnetic cylinder head, including at least two poles angularly offset by a substantially equal angle value.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
Simple homopolar stator machines supplied with alternating current are known from the state of the art. The structure and operation of such an electric machine, also called transverse flux electric machine, are widely described in the literature. They are all based on structures where the electric coils have an annular shape. Said annular arrangement is interesting from a manufacturing perspective, but detrimental to performance, since it generates a very significant leakage flux, and therefore limits the performance at high speeds, due to the inductive nature of the machine.
FIG. 1 shows the prior art for said simple homopolar structure, in an octopolar version, with a three-phase claw stator and rotor with surface magnets. Another embodiment may include a rotor with buried magnets. Another embodiment may include a polyphase stator, there being any number of structural phases (greater than or equal to the unit). Another embodiment may include an inverted external rotor.
The embodiment of FIG. 1 includes three identical stators (c1), (c2) and (c3) forming a three-phase simple homopolar machine (c0). Said stators (c1), (c2) and (c3) will be referred to as structural phases in this document when they are complete with their coil (c4), (c5) or (c6). These structural phases are phase-shifted relative to one another by a mechanical angle of about 30° for a three-phase version. In the case of the embodiment shown in FIG. 1, the angle (c10), phase shift angle between phase (c1) and phase (c2), is substantially equal to 30°, and the angle (c11), phase shift angle between structural phase (c1) and structural phase (c3), is substantially equal to 60°. The angle (c10) substantially corresponds to one third of the electrical angle of the rotary machine, said electrical angle being equal to 360° (one revolution) divided by the number of pairs of poles (four in this octopolar case). The angle (c11) is substantially equal to twice the angle (c10).
These angular phase shifts may be different, based on the applications, but these variations belong to the known state of the art, applied to other rotary machine structures in particular. They are used only to optimize the final rotary machine. A two-phase version of said rotary machine would include only two stators (c1) and (c2), which would then be offset by an angle (c10) equal to 45° in the octopolar embodiment described in FIG. 1. The rules for calculating the angular phase offsets between structural phases, or respective stators, are part of the state of the art. In a poly-phase version, in general, the number of power supply phases is at least equal to the number of structural phases (stators) (c1), (c2), (c3).
In the embodiment of FIG. 1, the stators (c1), (c2) and (c3) can have a claw or undulating structure (made with twisted sheet metal), which is characterized by a visible undulation of the stator coils, respectively denoted (c4), (c5) and (c6) around rotation planes X/Y (c12) of each stator. Said undulation can be obtained by twisting stator teeth, as proposed by French patent application no. 2,809,240, or by encircling coils (c4), (c5) and (c6) as proposed by French patent application no. 2,828,027.
In this last, clever embodiment, shown in FIG. 2 for a number of poles equal to 28, the stators (c1), (c2) and (c3) are all made in the same way (b10), from two identical claws (b1) and (b2), gripping a coil (b3). Said claws are assembled on one another, according to patent application no. 2,828,027, such that their respective teeth (b4) and (b5) of the two claws (b1) and (b2) are substantially equidistant. The claw (b1) is placed on the claw (b2), as indicated by arrow (b7). The contact zones (b30) between the claws (b1) and (b2) must be made correctly, so as to avoid unwanted magnetic air gaps in the contact zone. The shape of this contact zone (b30) may not be made up of a coplanar plane along X/Y (c12), but may adopt any other shape, such as an undulation or a crenulation, that would allow the relative angular wedging of said claws (b1) and (b2). The claw (b2) is angularly offset relative to the claw (b1). In the case of the stator of FIG. 2, said wedging angle (b6) is substantially equal to half the electrical angle the machine, i.e., for this polarity of 14 pairs of poles shown in FIG. 2, the value of 12.857°.
It is important to note that the embodiments of FIGS. 1 and 2 consider that each tooth (b4) and (b5) forms a complete electric pole of the machine. In FIG. 1, we consequently have an assembly of mono-phase rotary electric machines, joined axially around a same rotor (c7). Said rotor may be of several types, in particular synchronous, asynchronous or with a variable reluctance. The different embodiments known at this time for rotors are part of the state of the art and all adapt to the presence of a set of claw stators, as described in FIG. 1.
In the rest of this document, we will refer to the stators (c1), (c2) and (c3) as structural phase, in order to clarify their role. Throughout the following description, we therefore consider the assembly formed by two claws (b1) and (b2), gripping a coil (b3), to form a complete structural phase. FIG. 3 more synthetically shows this proposal, by showing these two claws (a10) for (b1), and (a11) for (b2), which are joined against one another along the direction (a13), to form a single phase (a14), shown in FIG. 4, like that (b10) described above in reference to FIG. 2 and corresponding to the joining of two claws (b1) and (b2), gripping a coil (b3). At this stage of the description of the state of the art, note should be made of the interest in providing axial maintaining means for the claws (b1) and (b2) on one another, which may for example consist of an elastic gripping washer, mounted in any location of the rotation axis of the plane XY (c12). The state of the art broadly describes the shapes of the teeth, in order to improve the air gap flux and reduce the leakage fluxes.
All of these descriptions of FIGS. 1 and 2 are part of the state of the art. They include the version with an inverted stator, where the teeth (b4) and (b5) of the claws (b1) and (b2) are situated on the outer periphery, with a rotor that is situated outside the stator.
FIG. 3 shows how two claws (a10) and (a11) generically form a structural phase (a14a) or (a14b), this structural phase indifferently being able to form a rotary electric machine armature or inductor, depending on whether the coil (a15) is encompassed internally by the claws (a10) and (a11). The case shown by embodiment (a14a) corresponds to a machine with a so-called inverse structure, with an external rotor, where the coil (a15) is placed inside the rotor. The case shown by embodiment (a14b) corresponds to a machine with a so-called direct structure, with an internal rotor, where the coil (a15) is placed outside the rotor.
The state of the art clearly shows that the various elements of an electric rotary machine are interchangeable, in particular their relative internal or external position, as shown by FIG. 4. The structural phase (a14), made up of two claws (a10) and (a11), can be situated outside a part (a22), to then form a direct mono-phase rotary machine (a20b). The structural phase (a14), made up of two claws (a10) and (a11), can be situated inside a part (a21), to then form an inverse mono-phase rotary machine (a20a). The axial juxtaposition of these complete machines (a20a) or (a20b), angularly offset by an adequate angle, as known from the state of the art explained above, makes it possible to form a polyphase rotary machine.
In the presentation of FIG. 4, the parts (a14), (a22) and (a21) may indifferently be static or rotary. If a rotary part (a14) includes an integral coil, it is then necessary to power it with rings or any other system known by those skilled in the art (for example, rotary diodes).
The (a14) static and (a22) rotary magnets (or coiled inductor) combination corresponds to a so-called direct synchronous machine (a20b). The structural phase (a14) is then supplied with alternating current and according to the so-called brushless control methods known by those skilled in the art.
The (a14) static and (a21) rotary magnets (or coiled inductor) combination corresponds to a machine (a20a) forming a so-called reverse synchronous machine. The structural phase (a14) is then supplied with alternating current and according to the so-called brushless control methods known by those skilled in the art.
The (a21) static and (a14) rotary combination corresponds to a machine (a20a) forming a claw alternator, called Lundell, widely used in heat engines.
Any other combinations are possible, such as (a14) rotary and (a22) static, or (a14) rotary and (a21) static, or both parts (a14) and (a22) rotary, or both parts (a14) and (a21) rotary. These different combinations are widely described in the state of the art for rotary machines with a coplanar structure.
FIG. 5 shows a state of the art for homopolar rotary machines powered with direct current. FIG. 5 shows the traditional structure of a machine with a homopolar rotor (also called transverse flux electric machine) where a coplanar tetrapolar polyphase stator (a1) is placed around a rotor separated into two half-rotors (a2) and (a3), angularly offset relative to one another by 90 mechanical degrees. The rotor excitation coil (a4) is situated in the median joining plane of the two half-rotors (a2) and (a3). Once supplied with direct current, the coil (a4) generates a magnetic flux denoted 4), which radially traverses the air gap separating the rotor from the stator across from the zones denoted S on the side of the rotor (a3) and across from the zones denoted N on the side of the rotor (a2). As a result, half of the conductors of the stator (a1) do not receive any rotor magnetic flux and therefore do not participate in generating motor torque.
The use of this machines topology has therefore been reduced to specific applications, where the rotor must for example rotate very quickly, or where the ambient operating temperature was incompatible with the traditional winding techniques. The most remarkable application of this technology consists of a cryogenic machine, where the ceramic winding could not withstand being rotated.
These homopolar structures generally have the primary flaw of providing half of the torque that a similar coplanar machine could provide. This it is the main reason for their low rate of industrial use. The homopolar machine described in the state of the art led to the so-called dual homopolar machine, described in a limited version in French patent no. FR 10 60923-1, which is made by assembling homopolar machines with annular coils, around an annular magnetizing central coil. The flaw of this dual homopolar machine lies in the elimination of every other magnetic pole in its rotor, which leads to a significant loss of torque.
The pole forms of the state of the art are varied, and in mono-phase machines may for example assume the form of protruding poles. A mono-phase machine with protruding poles is then formed by one or two assemblies (g10) as described in FIGS. 6 and 7. In one version (g5), a part (g1) made from a ferromagnetic material receives a winding that may be interleaved (g3) or, in one version (g6), undulated (g4). The interleaved winding (g3) is characterized by the fact that each turn performs several revolutions around a same pole (g2), before going to the next pole (g2). An undulated winding (g4) is characterized by the fact that each turn passes around all of the poles (g2) of the part (g1) before returning to the same pole (g2). An undulated-interleaved combination is possible, and abundantly described by the state of the art.
The part (g1) is associated with a part (g13) that includes magnets (g12) or a winding surrounding polar parts (g12). As shown in FIG. 7, the right assembly (g10), enlarged in (g11) in the left part of the figure, forms a dual-protrusion mono-phase machine, where the current in the different windings can be direct or alternating. The assembly formed by (g12) and (g13) can be made by using a smooth pole structure, as abundantly described by the state of the art, through notches traversed by electric windings. The parts (g13) may either be internal or external with respect to the parts (g1).
It is possible to demonstrate that the so-called homopolar structures (a20a) and (a20b) of FIG. 4 are in fact mono-phase machines, which proceed from the same generic topology as (g1), as shown in FIGS. 6 and 7.
As previously indicated, the present invention relates to rotary electric machines with a homopolar structure (also called transverse flux electric machines), composite or the like. The rotary electric machines with a homopolar structure traditionally includes a stator and a rotor, at least the stator or the rotor being made up of at least one electric coil supported by a magnetic cylinder head. The rotary electric machine according to the present invention additionally includes at least two poles angularly offset by a substantially equal angular value. These poles can be made up of tabs or teeth secured to said annular cylinder head and bent parallel to the rotation axis of the machine, or by protuberances secured to said annular cylinder head, or made by notches arranged in the cylinder head, receiving conductors.
There may be multiple rotary parts, called rotors in the descriptions that follow, as well as multiple stationary parts, called stators. It is then possible to form a rotary electric machine including a single stator, or group of stators, associated with a single rotor, or several rotors or groups of rotors. By extension, it is possible to form a rotary electric machine including any number of stators or groups of stators, associated with any number of rotors or groups of rotors.
In this document, the notion of group of stators or rotors corresponds to the notion of electric phases. A polyphase rotary electric machine includes Npe electric phases, i.e., including Npe groups of independent coils, powered by an appropriate polyphase system. Said polyphase rotary electric machine is formed by Npe groups of elementary mono-phase rotary electric machines.
Throughout the following description, the rotors and stators can be mounted directly with the rotor inside the stator, or conversely, with the rotor outside the stator. Throughout the descriptions, the armatures and the inductors may be placed at the rotor and/or stator.